Salts of hiv inhibitor compounds

ABSTRACT

The invention is related to salts of anti-viral compounds, compositions containing such salts, and therapeutic methods that include the administration of such salts, as well as to processes and intermediates useful for preparing such salts.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is filed under 35 U.S.C. 111(a) claiming the benefitunder 35 U.S.C. 119(e) of U.S. provisional application 61/078,989, filedJul. 8, 2008 which is herein incorporated by reference in its entiretyfor all purposes.

FIELD OF THE INVENTION

The invention relates generally to salts of compounds with antiviralactivity and more specifically with anti-HIV properties.

BACKGROUND OF THE INVENTION

Human immunodeficiency virus (HIV) is a retrovirus that can lead toacquired immunodeficiency syndrome (AIDS), a condition in humans inwhich the immune system is weakened, leading to life-threateningopportunistic infections. Inhibitors of HIV are useful to treat HIVinfection in a mammal (e.g., reduce and limit the establishment andprogression of infection by HIV) as well as in diagnostic assays forHIV. The usefulness of currently marketed inhibitors of HIV is to someextent limited by toxicity and other side effects. Thus, there is a needfor new HIV therapeutic agents.

A pharmaceutical formulation of a therapeutic agent must reproduciblyand consistently deliver the therapeutic agent to a patient in needthereof. This consistency of delivery can be achieved, at least in part,by incorporation of a stable, soluble, solid-state form of thetherapeutic agent into the pharmaceutical composition. Moreover, thesynthesis of the desired solid-state form of the therapeutic agentshould be technically and economically feasible, and should be suitablefor full-scale commercial production.

SUMMARY OF THE INVENTION

EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninateis a reverse transcriptase inhibitor that blocks the replication of HIVviruses, in vivo and in vitro, and has limited undesirable side effectswhen administered to human beings. The structure of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninateis shown in Formula P:

EthylN-[(S)({[2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninateis a low melting point, amorphous, solid which is difficult to isolate,purify, store for an extended period, and formulate as a pharmaceuticalcomposition. EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninateis also a weak base that is capable of forming salts with acids.Accordingly, in one aspect, the present invention provides stable saltsof EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninatethat are more physically stable, and are more readily isolated andformulated, than the free base form of the compound.

The salts of the present invention are useful, for example, for treatinghuman patients infected with human immunodeficiency virus (strains ofHIV-1 or HIV-2) which causes AIDS. The salts of the present inventionare also useful, for example, for preparing a medicament for treatingHIV or an HIV associated disorder. The salts of the present inventionare also useful, for example, for inhibiting the replication of HIVviruses in vitro, and can be used, therefore, in biological assays as acontrol compound for identifying other reverse transcriptase inhibitors,or for investigating the mechanism of action of HIV reversetranscriptase and its inhibition.

Thus, in one aspect, the present invention provides citrate, succinateand malonate salts of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate,and methods of making the foregoing salts. In some embodiments, thesalts of the present invention are anhydrous, while in other embodimentsthe salts of the present invention are at least partially hydrated. Insome embodiments, the salts of the present invention exist ascrystalline forms.

Thus, the present invention comprises citrate, succinate and malonatesalts of the compound of Formula P, as well as hydrates thereof. Theinventive hydrates may be in a partial (e.g., hemi-hydrate) or fullhydrated state (e.g., mono-hydrate). The present invention alsocomprises the subject salts in anhydrous or essentially anhydrousstates. Similarly, the inventive salts and hydrates thereof compriseamorphous and crystalline states, as well as states comprising bothamorphous and crystalline characteristics. As used herein, “crystalline”means a material that has an ordered, long range molecular structure. Incontrast, “amorphous” materials do not possess long range order. It isunderstood that crystalline materials are generally more stablethermodynamically than amorphous forms of the same substance. Thus, withonly a few notable exceptions, it is generally preferred to usecrystalline materials in pharmaceutical applications. A measure of thedegree of crystallinity of the inventive compounds can be seen, forexample, in the sharpness of the DSC and XRPD absorption bands (peaks).The sharper the peak, the higher the degree of crystallinity.Conversely, the broader the peak, the lower the degree of crystallinity.

As described more fully in Example 12 herein, in specific embodiments, acitrate salt of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninateis characterized by absorption bands, obtained from an X-ray powderdiffraction pattern, at spectral d-spacings of 4.48, 3.12 and 6.05angstroms; a succinate salt of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninateis characterized by absorption bands, obtained from an X-ray powderdiffraction pattern, at spectral d-spacings of 3.57, 4.80 and 4.99angstroms; and a malonate salt of Ethyl.N-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninateis characterized by absorption bands, obtained from X-ray powderdiffraction pattern, at spectral d-spacings of 4.99, 5.93 and 4.72angstroms. In another specific embodiment, the present inventionprovides a citrate salt of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninatehaving a melting point of from 142° C. to 150° C.

EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninateis an amidate prodrug which undergoes reaction with and decomposition inprotic solvents. The rate of the reaction depends on pH and temperature.Consequently, the formation of a stable salt between the amidate prodrugand citric acid, succinic acid and/or malonic acid, which each containnucleophilic moieties capable of reacting with the prodrug (e.g.,reaction with the amidate moiety of the prodrug) is a surprising andunexpected result.

In another aspect, the present invention provides pharmaceuticalcompositions that each include a therapeutically effective amount of asalt of the present invention and a pharmaceutically acceptable carrieror excipient. Pharmaceutical compositions of the present invention mayalso include an additional therapeutic agent, such as an antiviral,antibacterial, antifungal or anticancer agent. The pharmaceuticalcompositions of the invention may be in the form of unit dosage forms,such as tablets or capsules. The unit dosage forms typically provide aneffective daily dose of a salt of the present invention to a human beingin need thereof. Effective daily doses of the salts of the presentinvention are typically from 1 mg to 100 mg, such as from 10 mg to 30mg.

In another aspect, the present invention provides methods of making thecitrate, succinate and malonate salts of the present invention. Thus,for example, the present invention provides a process for preparing acitrate salt of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate,wherein the process includes the step of contacting about one equivalentof EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninatefree base in a suitable solvent (e.g., acetonitrile) with form about oneequivalent to about 1.2 equivalents of citric acid at a temperature inthe range of from about 55° C. to about 75° C.

The present invention also provides a process for preparing a succinatesalt of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate,wherein the process includes the step of contacting about one equivalentof EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninatefree base in a suitable solvent (e.g., 2-butanone) with from about oneequivalent to about 1.2 equivalents of succinic acid at a temperature inthe range of from about 60° C. to about 70° C. to form the succinatesalt of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate.

Further, the present invention provides a process for preparing amalonate salt of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate,wherein the process includes the step of contacting about one equivalentof EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninatefree base in a suitable solvent (e.g., 2-butanone) with from about oneequivalent to about 1.2 equivalents of malonic acid at a temperature inthe range of from about 50° C. to about 70° C. to form the malonate saltof EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate.

In a further aspect, the present invention provides methods of treatingor prophylactically preventing AIDS, wherein the methods include thestep of administering to a human being suffering from AIDS atherapeutically effective amount of a salt of the invention, or ahydrate thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a characteristic differential scanning calorimetry (DSC)trace for the malonate salt of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate.

FIG. 2 shows a characteristic DSC trace for the succinate salt of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate.

FIG. 3 shows a characteristic DSC trace for the citrate salt of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate.

FIG. 4 shows a characteristic X-ray powder diffraction (XRPD) patternfor the malonate salt of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate.

FIG. 5 shows a characteristic XRPD pattern for the succinate salt ofEthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate

FIG. 6 shows a characteristic XRPD pattern for the citrate salt of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

When tradenames are used herein, applicants intend to independentlyinclude the tradename product and the active pharmaceuticalingredient(s) of the tradename product.

Salts of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate

In one aspect, the present invention provides citrate, succinate andmalonate salts of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate.

The citrate salt is shown in Formula I:

The succinate salt is shown in Formula II:

The malonate salt is shown in Formula III:

A method for synthesizing EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninateis described in Example 1 herein. Methods for making the malonate,succinate and citrate salts of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninateare described in Examples 3, 4 and 5, respectively, herein. Somephysical properties of the foregoing salts are described in Example 6herein and demonstrate, for example, that each of these salts isphysically stable when stored at 40° C. and a relative humidity of 75%.

The citrate, succinate and malonate salts of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninateare useful, for example, for inhibiting the replication of HIV in vitroand in vivo. In this regard, as explained more fully in Example 8herein, EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninateis a prodrug that is metabolized in the human body to yield a parentcompound which, in turn, is phosphorylated within the body to producethe active metabolite that inhibits HIV replication. Example 8 hereinshows that EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninatecauses a greater accumulation of the active metabolite in white bloodcells, which are the cells that harbor the HIV virus, than does theparent compound. Further, Example 9 herein presents in vitro datashowing that EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninateis a more potent anti-HIV drug than the parent compound as assessed inan in vitro assay. Additionally, Example 10 herein provides data showingthat a tablet containing the citrate salt of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninateprovides this drug to the bloodstream of Beagle dogs with similarpharmacokinetics to a liquid preparation of the drug administeredorally. Thus, the citrate salt of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninateis a physically and chemically stable composition of matter that can beadministered orally to a living subject, to provide a therapeuticallyeffective amount of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate,which is a more effective anti-HIV agent than the parent compound.

Pharmaceutical Compositions

In another aspect, the present invention provides pharmaceuticalcompositions, also referred to as pharmaceutical formulations thatinclude a therapeutically effective amount of one or more salts of theinvention, and a pharmaceutically acceptable carrier or excipient.

While it is possible for the salts of the invention to be administeredalone, it is typically preferable to administer them as pharmaceuticalcompositions. The pharmaceutical compositions of the invention areformulated with conventional carriers and excipients, which are selectedin accord with ordinary practice. The carrier(s) must be “acceptable” inthe sense of being compatible with the other ingredients of theformulation and physiologically innocuous to the recipient thereof.Tablets contain such components as excipients, glidants, fillers,binders and the like. Aqueous formulations are prepared in sterile form,and when intended for delivery by other than oral administration theyare generally isotonic. All formulations optionally contain excipientssuch as those set forth in the Handbook of Pharmaceutical Excipients (R.C. Rowe et al., Pharmaceutical Press, 5^(th) ed., 2006). Excipientsinclude ascorbic acid and other antioxidants, chelating agents such asEDTA, carbohydrates such as dextrin, hydroxyalkylcellulose,hydroxyalkylmethylcellulose, stearic acid and the like. The pH of theformulations ranges from about 3 to about 11, but is ordinarily about 7to 10.

The formulations may conveniently be presented in unit dosage form(e.g., tablet) and may be prepared by any of the methods well known inthe art of pharmacy. Techniques and formulations generally are found inRemington's Pharmaceutical Sciences (Mack Publishing Co., Easton, Pa.).Such methods include the step of bringing into association the activeingredient with the carrier which constitutes one or more accessoryingredients. In general the formulations are prepared by uniformly andintimately bringing into association the active ingredient with liquidcarriers or finely divided solid carriers or both, and then, ifnecessary, shaping the product.

Pharmaceutical formulations containing the active ingredient may be inany form suitable for the intended method of administration. When usedfor oral use for example, tablets, troches, lozenges, aqueous or oilsuspensions, dispersible powders or granules, emulsions, hard or softcapsules, syrups or elixirs may be prepared. Compositions intended fororal use may be prepared according to any method known to the art forthe manufacture of pharmaceutical compositions and such compositions maycontain one or more agents including sweetening agents, flavoringagents, coloring agents and preserving agents, in order to provide apalatable preparation. Tablets containing the active ingredient inadmixture with non-toxic pharmaceutically acceptable excipient which aresuitable for manufacture of tablets are acceptable. These excipients maybe, for example, inert diluents, such as calcium or sodium carbonate,lactose, lactose monohydrate, croscarmellose sodium, povidone, calciumor sodium phosphate; granulating and disintegrating agents, such asmaize starch, or alginic acid; binding agents, such as cellulose,microcrystalline cellulose, starch, gelatin or acacia; and lubricatingagents, such as magnesium stearate, stearic acid or talc. Tablets may beuncoated or may be coated by known techniques includingmicroencapsulation to delay disintegration and adsorption in thegastrointestinal tract and thereby provide a sustained action over alonger period. For example, a time delay material such as glycerylmonostearate or glyceryl distearate alone or with a wax may be employed.

Formulations for oral use may be also presented as hard gelatin capsuleswhere the active ingredient is mixed with an inert solid diluent, forexample calcium phosphate or kaolin, or as soft gelatin capsules whereinthe active ingredient is mixed with water or an oil medium, such aspeanut oil, liquid paraffin or olive oil.

Aqueous suspensions of salts of the invention contain the activematerials in admixture with excipients suitable for the manufacture ofaqueous suspensions. Such excipients can include a suspending agent,such as sodium carboxymethylcellulose, methylcellulose, hydroxypropylmethylcellulose, sodium alginate, polyvinylpyrrolidone, gum tragacanthand gum acacia, and dispersing or wetting agents such as a naturallyoccurring phosphatide (e.g., lecithin), a condensation product of analkylene oxide with a fatty acid (e.g., polyoxyethylene stearate), acondensation product of ethylene oxide with a long chain aliphaticalcohol (e.g., heptadecaethyleneoxycetanol), a condensation product ofethylene oxide with a partial ester derived from a fatty acid and ahexitol anhydride (e.g., polyoxyethylene sorbitan monooleate). Theaqueous suspension may also contain one or more preservatives such asethyl or n-propyl p-hydroxy-benzoate, one or more coloring agents, oneor more flavoring agents and one or more sweetening agents, such assucrose or saccharin.

Oil suspensions may be formulated by suspending the active ingredient ina vegetable oil, such as arachis oil, olive oil, sesame oil or coconutoil, or in a mineral oil such as liquid paraffin. The oral suspensionsmay contain a thickening agent, such as beeswax, hard paraffin or cetylalcohol. Sweetening agents, such as those set forth above, and flavoringagents may be added to provide a palatable oral preparation. Thesecompositions may be preserved by the addition of an antioxidant such asascorbic acid.

Dispersible powders and granules of the invention suitable forpreparation of an aqueous suspension by the addition of water providethe active ingredient in admixture with a dispersing or wetting agent, asuspending agent, and one or more preservatives. Suitable dispersing orwetting agents and suspending agents are exemplified by those disclosedabove. Additional excipients, for example sweetening, flavoring andcoloring agents, may also be present.

The pharmaceutical compositions of the invention may also be in the formof oil-in-water emulsions. The oily phase may be a vegetable oil, suchas olive oil or arachis oil, a mineral oil, such as liquid paraffin, ora mixture of these. Suitable emulsifying agents includenaturally-occurring gums, such as gum acacia and gum tragacanth,naturally occurring phosphatides, such as soybean lecithin, esters orpartial esters derived from fatty acids and hexitol anhydrides, such assorbitan monooleate, and condensation products of these partial esterswith ethylene oxide, such as polyoxyethylene sorbitan monooleate. Theemulsion may also contain sweetening and flavoring agents. Syrups andelixirs may be formulated with sweetening agents, such as glycerol,sorbitol or sucrose. Such formulations may also contain a demulcent, apreservative, a flavoring or a coloring agent.

The pharmaceutical compositions of the invention may be in the form of asterile injectable preparation, such as a sterile injectable aqueous oroleaginous suspension. This suspension may be formulated according tothe known art using those suitable dispersing or wetting agents andsuspending agents which have been mentioned above. The sterileinjectable preparation may also be a sterile injectable solution orsuspension in a nontoxic parenterally acceptable diluent or solvent,such as a solution in 1,3-butane-diol or prepared as a lyophilizedpowder. Among the acceptable vehicles and solvents that may be employedare water, Ringer's solution and isotonic sodium chloride solution. Inaddition, sterile fixed oils may conventionally be employed as a solventor suspending medium. For this purpose any bland fixed oil may beemployed including synthetic mono- or diglycerides. In addition, fattyacids such as oleic acid may likewise be used in the preparation ofinjectables.

The amount of active ingredient that may be combined with the carriermaterial to produce a single dosage form will vary depending, forexample, upon the particular mode of administration. For example, atime-release formulation intended for oral administration to humans maycontain approximately 1 to 1000 mg of active material compounded with anappropriate and convenient amount of carrier material which may varyfrom about 5 to about 95% of the total composition (weight:weight).

Formulations suitable for administration to the eye include eye dropswherein the active ingredient is dissolved or suspended in a suitablecarrier, especially an aqueous solvent for the active ingredient.

Formulations suitable for topical administration in the mouth includelozenges comprising the active ingredient in a flavored basis, such assucrose and acacia or tragacanth; pastilles comprising the activeingredient in an inert basis such as gelatin and glycerin, or sucroseand acacia; and mouthwashes comprising the active ingredient in asuitable liquid carrier.

Formulations for rectal administration may be presented as a suppositorywith a suitable base comprising for example cocoa butter or asalicylate.

Formulations suitable for intrapulmonary or nasal administration have aparticle size for example in the range of 0.1 to 500 microns (includingparticle sizes in a range between 0.1 and 500 microns in increments ofmicrons such as 0.5, 1, 30 microns, 35 microns, etc.), which isadministered by rapid inhalation through the nasal passage or byinhalation through the mouth so as to reach the alveolar sacs. Suitableformulations include aqueous or oily solutions of the active ingredient.Formulations suitable for aerosol or dry powder administration may beprepared according to conventional methods and may be delivered withother therapeutic agents such as compounds heretofore used in thetreatment or prophylaxis of conditions associated with HIV activity.

Formulations suitable for vaginal administration may be presented aspessaries, tampons, creams, gels, pastes, foams or spray formulationscontaining in addition to the active ingredient such carriers as areknown in the art to be appropriate.

Formulations suitable for parenteral administration include aqueous andnon-aqueous sterile injection solutions which may contain anti-oxidants,buffers, bacteriostats and solutes which render the formulation isotonicwith the blood of the intended recipient; and aqueous and non-aqueoussterile suspensions which may include suspending agents and thickeningagents.

The formulations are presented in unit-dose or multi-dose containers,for example sealed ampoules and vials, and may be stored in afreeze-dried (lyophilized) condition requiring only the addition of thesterile liquid carrier, for example water for injection, immediatelyprior to use. Extemporaneous injection solutions and suspensions areprepared from sterile powders, granules and tablets of the kindpreviously described. Preferred unit dosage formulations are thosecontaining a daily dose or unit daily sub-dose or an appropriatefraction thereof, of the active ingredient. Thus, for example, a dailydose of a salt of the present invention can be provided in a singletablet, or in multiple tablets (e.g., two or three tablets).

It should be understood that in addition to the ingredients particularlymentioned above the formulations of this invention may include otheragents conventional in the art having regard to the type of formulationin question, for example those suitable for oral administration mayinclude flavoring agents.

Pharmaceutical formulations that are also within the scope of theinvention provide controlled release of the active ingredient to allowless frequent dosing or to improve the pharmacokinetic or toxicityprofile of the active ingredient. Accordingly, the invention alsoprovides pharmaceutical compositions comprising one or more salts of theinvention formulated for sustained or controlled release.

An effective dose of a salt of the present invention depends, forexample, on whether the salt is being used prophylactically (typically alower dose is required compared to therapeutic use of the same salt),the method of delivery, and the pharmaceutical formulation, and will bedetermined by the clinician using conventional dose escalation studies.An effective dose can be expected to be from about 0.0001 mg/kg bodyweight per day to about 100 mg/kg body weight per day. Typically, fromabout 0.01 to about 10 mg/kg body weight per day. More typically, fromabout 0.01 to about 5 mg/kg body weight per day. More typically, fromabout 0.05 to about 0.5 mg/kg body weight per day. For example, thedaily dose for an adult human of approximately 70 kg body weight willtypically range from 1 mg to 1000 mg, preferably between 5 mg and 500mg, and may take the form of single or multiple doses. By way ofexample, the dose of a salt of the present invention in a unit doseformulation to be administered once per day may be from 1 mg to 100 mg,such as from 30 mg to 60 mg, such as a 30 mg daily dose or a 60 mg dailydose.

Combination Therapy

Each of the citrate, succinate and malonate salts of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninatemay be employed in combination with other therapeutic agents for thetreatment or prophylaxis of AIDS and/or one or more other diseasespresent in a human subject suffering from AIDS (e.g., bacterial and/orfungal infections, other viral infections such as hepatitis B orhepatitis C, or cancers such as Kaposi's sarcoma). The additionaltherapeutic agent(s) may be coformulated with one or more salts of theinvention (e.g., coformulated in a tablet).

Examples of such additional therapeutic agents include agents that areeffective for the treatment or prophylaxis of viral, parasitic orbacterial infections, or associated conditions, or for treatment oftumors or related conditions, include 3′-azido-3′-deoxythymidine(zidovudine, AZT), 2′-deoxy-3′-thiacytidine (3TC),2′,3′-dideoxy-2′,3′-didehydroadenosine (D4A),2′,3′-dideoxy-2′,3′-didehydrothymidine (D4T), carbovir (carbocyclic2′,3′-dideoxy-2′,3′-didehydroguanosine), 3′-azido-2′,3′-dideoxyuridine,5-fluorothymidine, (E)-5-(2-bromovinyl)-2′-deoxyuridine (BVDU),2-chlorodeoxyadenosine, 2-deoxycoformycin, 5-fluorouracil,5-fluorouridine, 5-fluoro-2′-deoxyuridine,5-trifluoromethyl-2′-deoxyuridine, 6-azauridine, 5-fluoroorotic acid,methotrexate, triacetyluridine,1-(2′-deoxy-2′-fluoro-1-(β-arabinosyl)-5-iodocytidine (FIAC),tetrahydro-imidazo(4,5,1-jk)-(1,4)-benzodiazepin-2(1H)-thione (TIBO),2′-nor-cyclicGMP, 6-methoxypurine arabinoside (ara-M), 6-methoxypurinearabinoside valerate; cytosine arabinoside (ara-C),2′,3′-dideoxynucleosides such as dideoxycytidine (ddC),2′,3′-dideoxyadenosine (ddA) and 2′,3′-dideoxyinosine (ddI); acyclicnucleosides such as acyclovir, penciclovir, famciclovir, ganciclovir,HPMPC, PMEA, PMEG, PMPA, PMPDAP, FPMPA, HPMPA, HPMPDAP,(2R,5R)-9->tetrahydro-5-(phosphonomethoxy)-2-furanyladenine,(2R,5R)-1->tetrahydro-5-(phosphonomethoxy)-2-furanylthymine; otherantivirals including ribavirin (adenine arabinoside),2-thio-6-azauridine, tubercidin, aurintricarboxylic acid,3-deazaneoplanocin, neoplanocin, rimantidine, adamantine, and foscarnet(trisodium phosphonoformate); antibacterial agents includingbactericidal fluoroquinolones (ciprofloxacin, pefloxacin and the like);aminoglycoside bactericidal antibiotics (streptomycin, gentamicin,amicacin and the like); β-lactamase inhibitors (cephalosporins,penicillins and the like); other antibacterials including tetracycline,isoniazid, rifampin, cefoperazone, claithromycin and azithromycin,antiparasite or antifungal agents including pentamidine(1,5-bis(4′-aminophenoxy)pentane), 9-deaza-inosine, sulfamethoxazole,sulfadiazine, quinapyramine, quinine, fluconazole, ketoconazole,itraconazole, Amphotericin B, 5-fluorocytosine, clotrimazole,hexadecylphosphocholine and nystatin; renal excretion inhibitors such asprobenicid; nucleoside transport inhibitors such as dipyridamole,dilazep and nitrobenzylthioinosine, immunomodulators such as FK506,cyclosporin A, thymosin α-1; cytokines including TNF and TGF-β;interferons including IFN-α, IFN-β, and IFN-γ; interleukins includingvarious interleukins, macrophage/granulocyte colony stimulating factorsincluding GM-CSF, G-CSF, M-CSF, cytokine antagonists including anti-TNFantibodies, anti-interleukin antibodies, soluble interleukin receptors,protein kinase C inhibitors and the like.

Examples of suitable active therapeutic agents or ingredients which canbe combined with the salts of the invention, and which have activityagainst HIV, include 1) HIV protease inhibitors, e.g., amprenavir,atazanavir, fosamprenavir, indinavir, lopinavir, ritonavir,lopinavir+ritonavir, nelfinavir, saquinavir, tipranavir, brecanavir,darunavir, TMC-126, TMC-114, mozenavir (DMP-450), JE-2147 (AG1776),AG1859, DG35, L-756423, RO0334649, KNI-272, DPC-681, DPC-684, andGW640385X, DG17, PPL-100, 2) a HIV non-nucleoside inhibitor of reversetranscriptase, e.g., capravirine, emivirine, delaviridine, efavirenz,nevirapine, (+) calanolide A, etravirine, GW5634, DPC-083, DPC-961,DPC-963, MIV-150, and TMC-120, TMC-278 (rilpivirine), efavirenz, BILR355 BS, VRX 840773, UK-453,061, RDEA806, 3) a HIV nucleoside inhibitorof reverse transcriptase, e.g., zidovudine, emtricitabine, didanosine,stavudine, zalcitabine, lamivudine, abacavir, amdoxovir, elvucitabine,alovudine, MIV-210, racivir (-FTC), D-d₄FC, emtricitabine, phosphazide,fozivudine tidoxil, fosalvudine tidoxil, apricitibine (AVX754),amdoxovir, KP-1461, abacavir+lamivudine, abacavir+lamivudine+zidovudine,zidovudine+lamivudine, 4) a HIV nucleotide inhibitor of reversetranscriptase, e.g., tenofovir, tenofovir disoproxilfumarate+emtricitabine, tenofovir disoproxilfumarate+emtricitabine+efavirenz, and adefovir, 5) a HIV integraseinhibitor, e.g., curcumin, derivatives of curcumin, chicoric acid,derivatives of chicoric acid, 3,5-dicaffeoylquinic acid, derivatives of3,5-dicaffeoylquinic acid, aurintricarboxylic acid, derivatives ofaurintricarboxylic acid, caffeic acid phenethyl ester, derivatives ofcaffeic acid phenethyl ester, tyrphostin, derivatives of tyrphostin,quercetin, derivatives of quercetin, S-1360, zintevir (AR-177),L-870812, and L-870810, MK-0518 (raltegravir), BMS-707035, MK-2048,BA-011, BMS-538158, GSK364735C, 6) a gp41 inhibitor, e.g., enfuvirtide,sifuvirtide, FB006M, TRI-1144, SPC3, DES6, Locus gp41, CovX, and REP 9,7) a CXCR4 inhibitor, e.g., AMD-070, 8) an entry inhibitor, e.g., SPO1A,TNX-355, 9) a gp120 inhibitor, e.g., BMS-488043 and BlockAide/CR, 10) aG6PD and NADH-oxidase inhibitor, e g, immunitin, 10) a CCRS inhibitor,e.g., aplaviroc, vicriviroc, INCB9471, PRO-140, INCB15050, PF-232798,CCR5 mAb004, and maraviroc, 11) an interferon, e.g., pegylatedrIFN-alpha 2b, pegylated rIFN-alpha 2a, rIFN-alpha 2b, IFN alpha-2b XL,rIFN-alpha 2a, consensus IFN alpha, infergen, rebif, locteron, AVI-005,PEG-infergen, pegylated IFN-beta, oral interferon alpha, feron,reaferon, intermax alpha, r-IFN-beta, infergen+actimmune, IFN-omega withDUROS, and albuferon, 12) ribavirin analogs, e.g., rebetol, copegus,levovirin, VX-497, and viramidine (taribavirin) 13) NS5a inhibitors,e.g., A-831 and A-689, 14) NS5b polymerase inhibitors, e.g., NM-283,valopicitabine, R1626, PSI-6130 (R1656), HIV-796, BILB 1941, MK-0608,NM-107, R7128, VCH-759, PF-868554, GSK625433, and XTL-2125, 15) NS3protease inhibitors, e.g., SCH-503034 (SCH-7), VX-950 (Telaprevir),ITMN-191, and BILN-2065, 16) alpha-glucosidase 1 inhibitors, e.g.,MX-3253 (celgosivir) and UT-231B, 17) hepatoprotectants, e.g., IDN-6556,ME 3738, MitoQ, and LB-84451, 18) non-nucleoside inhibitors of HIV,e.g., benzimidazole derivatives, benzo-1,2,4-thiadiazine derivatives,and phenylalanine derivatives, 19) other drugs for treating HIV, e.g.,zadaxin, nitazoxanide (alinea), BIVN-401 (virostat), DEBIO-025,VGX-410C, EMZ-702, AVI 4065, bavituximab, oglufanide, PYN-17,KPE02003002, actilon (CPU-10101), KRN-7000, civacir, GI-5005, ANA-975(isatoribine), XTL-6865, ANA 971, NOV-205, tarvacin, EHC-18, and NIM811,19) pharmacokinetic enhancers, e.g., BAS-100 and SPI452, 20) RNAse Hinhibitors, e.g., ODN-93 and ODN-112, 21) other anti-HIV agents, e.g.,VGV-1, PA-457 (bevirimat), ampligen, HRG214, cytolin, polymun, VGX-410,KD247, AMZ 0026, CYT 99007, A-221 HIV, BAY 50-4798, MDX010 (iplimumab),PBS119, ALG889, and PA-1050040.

Again by way of example, the following list discloses exemplary HIVantivirals, with their corresponding U.S. patent numbers that can becombined with the salts of the present invention.

Exemplary HIV Antivirals and Patent Numbers

Ziagen (Abacavir sulfate, U.S. Pat. No. 5,034,394)Epzicom (Abacavir sulfate/lamivudine, U.S. Pat. No. 5,034,394)Hepsera (Adefovir dipivoxil, U.S. Pat. No. 4,724,233)Agenerase (Amprenavir, U.S. Pat. No. 5,646,180)Reyataz (Atazanavir sulfate, U.S. Pat. No. 5,849,911)Rescriptor (Delavirdine mesilate, U.S. Pat. No. 5,563,142)Hivid (Dideoxycytidine; Zalcitabine, U.S. Pat. No. 5,028,595)Videx (Dideoxyinosine; Didanosine, U.S. Pat. No. 4,861,759)Sustiva (Efavirenz, U.S. Pat. No. 5,519,021)Emtriva (Emtricitabine, U.S. Pat. No. 6,642,245)Lexiva (Fosamprenavir calcium, U.S. Pat. No. 6,436,989)Virudin; Triapten; Foscavir (Foscarnet sodium, U.S. Pat. No. 6,476,009)Crixivan (Indinavir sulfate, U.S. Pat. No. 5,413,999)Epivir (Lamivudine, U.S. Pat. No. 5,047,407)Combivir (Lamivudine/Zidovudine, U.S. Pat. No. 4,724,232)

Aluviran (Lopinavir)

Kaletra (Lopinavir/ritonavir, U.S. Pat. No. 5,541,206)Viracept (Nelfinavir mesilate, U.S. Pat. No. 5,484,926)Viramune (Nevirapine, U.S. Pat. No. 5,366,972)Norvir (Ritonavir, U.S. Pat. No. 5,541,206)Invirase; Fortovase (Saquinavir mesilate, U.S. Pat. No. 5,196,438)Zerit (Stavudine, U.S. Pat. No. 4,978,655)Truvada (Tenofovir disoproxil fumarate/emtricitabine, U.S. Pat. No.5,210,085)

Aptivus (Tipranavir)

Retrovir (Zidovudine; Azidothymidine, U.S. Pat. No. 4,724,232)

Methods of Inhibition of HIV

In a further aspect, the present invention provides methods of treatingAcquired immune Deficiency Syndrome (AIDS), wherein each method includesthe step of administering to a human being suffering from AIDS atherapeutically effective amount of a salt of the invention, or ahydrate of a salt of the invention. Treatment of AIDS includes theamelioration of at least one symptom of AIDS, and/or slowing orpreventing the progression of the disease. Typically the therapeuticallyeffective amount of the salt is administered to a human being in theform of a pharmaceutical composition, as described under the heading“Pharmaceutical Compositions”. Typically, the pharmaceutical compositionis administered orally, for example in the form of a tablet. Examples oftherapeutically effective daily doses of one or more salts of theinvention, or hydrates thereof, are from 1 mg to 100 mg, such as from 10mg to 30 mg. The salts of the invention can be administered daily, forexample in the form of one or more tablets that include an amount ofsalt that provides an effective amount, such as 10 mg or 30 mg or 60 mg,of the free base when the salt dissociates in an aqueous medium withinthe human body.

Routes of Administration

One or more salts of the invention are administered by any routeappropriate to the condition to be treated. Suitable routes includeoral, rectal, nasal, topical (including buccal and sublingual), vaginaland parenteral (including subcutaneous, intramuscular, intravenous,intradermal, intrathecal and epidural), and the like. It will beappreciated that the preferred route may vary with, for example, thecondition of the recipient. An advantage of the salts of the presentinvention is that they are orally bioavailable and can be dosed orally.

EXAMPLES AND EXEMPLARY EMBODIMENTS

See also WO 2006/110157, the disclosure of which is herein incorporatedby reference in its entirety, particularly, pages 167-174.

Example 1 Synthesis of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate

2-deoxy-2-fluoro-3,5-di-O-benzoyl-a-D-arabinofuranosylbromide (2)

Compound (2) was synthesized according to the synthetic schemesdisclosed in Tann et. al., JOC, 1985, Vol. 50 pg. 3644 and Howell et.al., JOC, 1988, Vol. 53, pg. 85.

To a solution of1.3.5-tri-O-benzoyl-2-deoxy-2-fluoro-alpha-D-arabinofuranose (1) (120 g,258 mmol), commercially available from Davos or CMS chemicals, in CH₂Cl₂(1 L) was added 33% HBr/Acetic acid (80 mL). The mixture was stirred atroom temperature for 16 h, cooled with ice-water, and slowly neutralizedover 1-2 h with NaHCO₃ (150 g/1.5 L solution).

The CH₂Cl₂ phase was separated and concentrated under reduced pressure.The residue was dissolved in ethyl acetate and washed with NaHCO₃ untilno acid was present. The organic phase was dried over MgSO₄, filteredand concentrated under reduced pressure to give product 2 as a yellowoil (˜115 g).

2-deoxy-2-fluoro-3,5-di-O-benzoyl-1-β-D-arabinofuranosyl-9H-6-ehloropurine(3)

Compound (3) was synthesized according to the synthetic schemesdisclosed in Ma et. al., J. Med. Chem., 1997, Vol. 40, pg. 2750; Marquezet. al., J. Med. Chem., 1990, Vol. 33, pg. 978; Hildebrand et. al., 3.Org. Chem., 1992, Vol. 57, pg. 1808 and Kazimierczuk et. al., JACS,1984, Vol. 106, pg. 6379.

To a suspension of NaH (14 g, 60%) in Acetonitrile (900 mL),6-chloropurine (52.6 g) was added in 3 portions. The mixture was stirredat room temperature for 1.5 h. A solution of 2 (258 mmol) inAcetonitrile (300 mL) was added dropwise. The resulting mixture wasstirred at room temperature for 16 h. The reaction was quenched withAcetic acid (3.5 mL), filtered and concentrated under reduced pressure.The residue was partitioned between CH₇Cl₂ and water. The organic phasewas dried over MgSO₄, filtered and concentrated. The residue was treatedwith CH₂Cl₂ and then EtOH (˜1:2 overall) to precipitate out the desiredproduct 3 as a yellowish solid (83 g, 65% from 1).

2-deoxy-2-fluoro-β-D-arabinofuranosyl-6-methoxyadenine (4)

To a suspension of 3 (83 g, 167 mmol) in Methanol (1 L) at 0° C., NaOMe(25% wt, 76 mL) was added. The mixture was stirred at room temperaturefor 2 h, and then quenched with Acetic acid (˜11 mL, pH=7). The mixturewas concentrated under reduced pressure and the resultant residuepartitioned between hexane and water (approximately 500 mL hexane and300 mL water). The aqueous layer was separated and the organic layermixed with water once again (approximately 300 mL). The water fractionswere combined and concentrated under reduced pressure to ˜100 mL. Theproduct, 4, precipitated out and was collected by filtration (42 g,88%).

2-deoxy-2-fluoro-5-carboxy-β-D-arabinofuranosyl-6-methoxyadenine (5)

Compound (5) was synthesized according to the synthetic schemesdisclosed in Moss et. al., J. Chem. Soc., 1963, pg. 1149.

A mixture of Pt/C (10%, 15 g (20-30% mol equiv.) as a water slurry) andNaHCO₃ (1.5 g, 17.94 mmol) in H₂O (500 mL) was stirred at 65° C. underH₂ for 0.5 h. The reaction mixture was then allowed to cool, placedunder a vacuum and flushed with N₂ several times to completely removeall H₂. Compound 4 (5.1 g, 17.94 mmol) was then added at roomtemperature. The reaction mixture was stirred at 65° C. under O₂(balloon) until the reaction was complete by LC-MS (typically 24-72 h).The mixture was cooled to room temperature and filtered. The Pt/C waswashed with H₂O extensively. The combined filtrates were concentrated to˜30 mL, and acidified (pH 4) by the addition of HCl (4N) at 0° C. Ablack solid precipitated out which was collected by filtration. Thecrude product was dissolved in a minimum amount of Methanol and filteredthrough a pad of silica gel (eluting with Methanol). The filtrate wasconcentrated and crystallized from water to give compound 5 (2.5 g) asan off-white solid.

(2′R, 3′S, 4′R, 5′R)-6-Methoxy-9-[tetrahydro4-iodo-3-fluoro-5-(diethoxyphosphinyl)methoxy-2-furanyl]purine (6)

Compound (6) was synthesized according to the synthetic schemesdisclosed in Zemlicka et. al., J. Amer. Chem., Soc., 1972, Vol. 94, pg.3213.

To a solution of 5 (22 g, 73.77 mmol) in DMF (400 mL), DMF dineopentylacetal (150 mL, 538 mmol) and methanesulfonic acid (9.5 mL, 146.6 mmol)were added. The reaction mixture was stirred at 80-93° C. (internaltemperature) for 30 min, then cooled to room temperature andconcentrated under reduced pressure. The residue was partitioned betweenethyl acetate and water. The organic phase was separated and washed withNaHCO₃ followed by brine, dried over MgSO₄, filtered and concentratedunder reduced pressure. The residue and diethyl(hydroxymethyl)phosphonate (33 mL, 225 mmol) were dissolved in CH₂Cl₂(250 mL) and cooled down to −40° C. A solution of iodine monobromide(30.5 g, 1.1 mol) in CH₂Cl₂ (100 mL) was added dropwise. The mixture wasstirred at −20 to −5° C. for 6 h. The reaction was then quenched withNaHCO₃ and Na₂S₂O₃. The organic phase was separated and the water phasewas extracted with CH₂Cl₂. The combined organic phases were washed withbrine, dried over MgSO₄, filtered and concentrated under reducedpressure. The residue was purified by silica gel chromatography to giveproduct 6 (6 g, 15.3%).

Alternative Procedure for the Preparation of 6

A solution of 5 (2.0 g, 6.7 mmol) in THF (45 mL) was treated withtriphenyl phosphine (2.3 g, 8.7 mmol) under N₂. Diisopropylazodicarboxylate (1.8 g, 8.7 mmol) was added slowly. The resultantmixture was stirred at room temperature for 1 h and then concentratedunder reduced pressure to dryness. The residue was dissolved in CH₂Cl₂(20 ml), and then treated with diethyl(hydroxymethyl)phosphonate (4.5 g,27 mmol). The mixture was cooled to −60° C. and then a cold solution ofiodine monobromide 2 g, 9.6 mmol) in CH₂Cl₂ (10 ml) was added. Thereaction mixture was warmed to −10° C. and then kept at −10° C. for 1 h.The reaction mixture was diluted with CH₂Cl₂, washed with saturatedaqueous NaHCO₃, and then with aqueous sodium thiosulfate. The organicphase was separated, dried over MgSO₄, and concentrated under reducedpressure to dryness. The reaction mixture was purified by silica gelchromatography (eluting with 25% ethyl acetate in CH₂Cl₂, then switchingto 3% methanol in CH₂Cl₂) to afford product 6 (0.9 g, 33%).

(2′R,5′R)-6-Methoxy-9-[3-fluoro-2,5-dihydro-5-(diethoxyphosphinyl)methoxy-2-furanyl]purine(7)

To a solution of compound 6 (6 g, 11.3 mmol) in acetic acid (2.5 mL) andmethanol (50 mL), NaClO (10-13%) (50 mL) was added dropwise. Thereaction mixture was then stirred for 0.5 h and concentrated underreduced pressure. The residue was treated with ethyl acetate and thenfiltered to remove solids. The filtrate was concentrated and the residuewas purified by silica gel chromatography to give product 7 (4 g, 88%).

(2′R, 5′R)-9-(3-fluoro-2,5-dihydro-5-phosphonomethoxy-2-furanyl)adeninedi sodium salt (8)

A solution of compound 7 (2.3 g, 5.7 mmol) in methanol (6 mL) was mixedwith ammonium hydroxide (28-30%) (60 mL). The resultant mixture wasstirred at 120° C. for 4 h, cooled, and then concentrated under reducedpressure. The residue was dried under vacuum for 12 h. The residue wasdissolved in DMF (40 mL) and bromotrimethylsilane (3.5 mL) was added.The mixture was stirred at room temperature for 16 h, and thenconcentrated under reduced pressure. The residue was dissolved inaqueous NaHCO₃ (2.3 g in 100 mL of water). The solution was evaporatedand the residue was purified on C-18 (40 μm) column, eluting with water.The aqueous fractions were freeze dried to give di-sodium salt 8 (1.22g, 57%).

Example of Monoamidate Preparation (9)

Di sodium salt 8 (25 mg, 0.066 mmol), (S)-Ala-O-cyclobutyl esterhydrochloride (24 mg, 2 eq., 0.133 mmol) and phenol (31 mg, 0.333 mmol)were mixed in anhydrous pyridine (1 mL). Triethylamine (111 μL, 0.799mmol) was added and the resultant mixture was stirred at 60° C. undernitrogen. In a separate flask, 2′-Aldrithiol (122 mg, 0.466 mmol) andtriphenylphosphine (103 mg, 0.466 mmol) were dissolved in anhydrouspyridine (0.5 mL) and the resulting yellow solution was stirred for15-20 min. The solution was then added to the solution of 8 in oneportion. The combined mixture was stirred at 60° C. under nitrogen for16 h to give a clear yellow to light brown solution. The mixture wasthen concentrated under reduced pressure. The resultant oil wasdissolved in CH₂Cl₂, and purified by silica gel chromatography (elutingwith a linear gradient of 0 to 5% MeOH in CH₂Cl₂) to give an oil. Theresulting oil was dissolved in acetonitrile and water and purified bypreparative HPLC (linear gradient, 5-95% acetonitrile in water). Purefractions were combined and freeze-dried to give mono amidate 9 as awhite powder.

Example of his Amidate Preparation (10)

Di sodium salt 8 (12 mg, 0.032 mmol) and (S)-Ala-O-n-Pr esterhydrochloride (32 mg, 6 eq., 0.192 mmol) were mixed in anhydrouspyridine (1 mL). Triethylamine (53 μL, 0.384 mmol) was added and theresultant mixture was stirred at 60° C. under nitrogen. In a separateflask, 2′-Aldrithiol (59 mg, 0.224 mmol) and triphenylphosphine (49 mg,0.224 mmol) were dissolved in anhydrous pyridine (0.5 mL) and theresulting yellow solution was stirred for 15-20 min. The solution wasthen added to the solution of 8 in one portion. The combined mixture wasstirred at 60° C. under nitrogen for 16 h to give a clear yellow tolight brown solution. The mixture was then concentrated under reducedpressure. The resultant oil was dissolved in CH₂Cl₂, and purified bysilica gel chromatography (eluting with a linear gradient of 0 to 5%MeOH in CH₂Cl₂) to give an oil. The resulting oil was dissolved inacetonitrile and water and purified by preparative HPLC (lineargradient, 5-95% acetonitrile in water). Pure fractions were combined andfreeze-dried to give his amidate as a white powder.

Example of Monoamidate Preparation (11)

Compound 8 (1.5 g, 4 mmol) was mixed with ethyl alanine ester HCl salt(1.23 g, 8 mmol) and phenol (1.88 g, 20 mmol). Anhydrous pyridine (35mL) was added followed by TEA (6.7 mL, 48 mmol). The mixture was stirredat 60° C. under nitrogen for 15-20 min. 2′-Aldrithiol (7.3 g) was mixedin a separate flask with triphenylphosphine (6.2 g) in anhydrouspyridine (5 mL) and the resultant mixture was stirred for 10-15 min togive a clear light yellow solution. The solution was then added to theabove mixture and stirred overnight at 60° C. The mixture wasconcentrated under reduced pressure to remove pyridine. The resultantresidue was dissolved in ethyl acetate and washed with saturated sodiumbicarbonate solution (2×) and then with saturated sodium chloridesolution. The organic layer was dried over sodium sulfate, filtered andthen concentrated under reduced pressure. The resultant oil wasdissolved in dichloromethane and loaded onto a dry CombiFlash column, 40g, eluting with a linear gradient of 0-5% methanol in dichloromethaneover 10 min and then 5% methanol in dichloromethane for 7-10 min.Fractions containing the desired product were combined and concentratedunder reduced pressure to give a foam. The foam was dissolved inacetonitrile and purified by prep HPLC to give 11 (0.95 g).

Dissolved 11 (950 mg) in small amount of acetonitrile and let stand atroom temperature overnight. Collected solid by filtration and washedwith small amount of acetonitrile. Filtrate was reduced under vacuum andthen loaded onto Chiralpak AS-H column equilibrated in Buffer A, 2%ethanol in acetonitrile. Isomer A, 12, was eluted out with Buffer A at10 mL/min for 17 mins. After which Buffer B, 50% methanol inacetonitrile, was used to elute isomer B, 13, separately out from thecolumn in 8 mins. Removed all solvent and then separately re-dissolvedin acetonitrile and water. Separately freeze-dried the samples (Mass-348mg). Isomer 12 is shown below

Example 2 Screening Salt Forms of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate

The following acids were screened to determine whether they formedsuitable crystalline salts of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate:Mineral acids (HX, wherein X=halogen; H₃PO₄); organic sulfonic acids(RSO₃H, wherein R=Me, Et, Ph, (t)-camphor-10-sulfonic acid;naphthalene-2-sulfonic acid; naphthalene-1,5-disulfonic acid); monocarboxylic acids (RCO₂H, wherein R═H, Me, Et, Ph, trans-PhCH═CH, Cl₂CH,PhCONHCH₂), and dicarboxylic acids (malonic, succinic, fumaric, adipic,oxalic, maleic).

Solids were obtained with three of the foregoing acids when mixed withEthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate:trifluoroacetic acid, malonic acid, and succinic acid. Trifluoroaceticacid is not considered to be pharmaceutically acceptable.

EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninateis an amidate prodrug which undergoes decomposition in protic solventsunder acidic or basic conditions. For this reason, acids withpotentially nucleophilic moieties were not included in the initial roundof screening.

Subsequently, citric acid, glycolic acid, (S)-(+)-lactic acid, salicylicacid, (S)-(−)-malic acid, (S)-(+)-mandelic acid and (S)-(+)-glutamicacid were evaluated. EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninateunexpectedly formed a stable crystalline salt with citric acid. This wasan unexpected result because citric acid includes a hydroxyl group whichcan act as a nucleophile toward the amidate moiety of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninateand potentially undergo a reaction therewith in which a covalent bond isformed between EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninateand the hydroxyl group of citric acid with the expulsion of eitherphenol or alanine ethyl ester.

Example 3 Synthesis of Malonate Salt of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate

The free base form of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninatewas dissolved in warm 2-butanone (15 parts), and malonic acid (0.26parts) was added to form a solution with agitation. Heptane (5 parts)was added to the solution which was slowly cooled to about 5° C.,collected and rinsed with cold 2-butanone/heptane. The resultingmalonate salt of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninatewas thereby produced with a yield of about 80%.

The NMR spectrum of the malonate salt had the following characteristics:¹H NMR (400 MHz, CHLOROFORM-d) ppm=8.27 (s, 1H), 8.26 (s, 1H), 7.32-7.20(m, 3H), 7.15 (d, J=7.8 Hz, 2H), 6.78 (m, 1H), 5.88 (br. s., 1H), 5.78(s, 1H), 4.17 (m, 2H), 4.15-4.07 (m, 3H), 3.85 (dd, J=8.0, 8.0, 1H),3.38 (s, 2H), 1.31 (d, J=7.0 Hz, 3H), 1.23 (t, J=7.0 Hz, 3H).

³¹P NMR (1.62 MHz, CHLOROFORM-d) ppm=20.64 (s).

¹⁹F NMR (376 MHz, ACETONITRILE-d3) ppm=−135.19 (s).

Example 4 Synthesis of Succinate Salt of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate

The free base form of Ethyl N-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninatewas dissolved in warm 2-butanone (15 parts), and succinic acid (0.28parts) was added to form a solution with agitation. The solution wasslowly cooled to about 5° C., collected, and rinsed with cold2-butanone, thereby yielding the succinate salt of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninateat a yield of 80%.

The NMR spectrum of the succinate salt had the followingcharacteristics: ¹H NMR (400 MHz, ACETONITRILE-d3) ppm=8.26 (s, 1H),8.15 (s, 1H), 7.29 (dd, J=7.6, 7.6 Hz, 2H), 7.16 (d, J=7.6 Hz, 1H), 7.12(d, J=8.0 Hz, 2H), 6.78 (m, 1H), 6.17 (br s, 1H), 5.89 (m, 2H),4.12-3.95 (overlapped multiplets, 6H), 2.53 (s, 4H), 1.24 (d, J=6.8,3H), 1.18 (t, J=7.2, 3H).

³¹P NMR (162 MHz, Acetonitrile-d3) ppm=21.60 (s).

¹⁹F NMR (376 MHz, Acetonitrile-d3) ppm=−135.19 (s).

Example 5 Synthesis of Citrate Salt of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate

The free base form of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate(about 30 g) was dissolved in hot acetonitrile (16 parts) and citricacid (0.38 parts) were added with agitation. The resulting solution wasslowly cooled to about 5° C., collected and rinsed with coldacetonitrile, and dried, thereby affording the citrate salt of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninatewith a yield of about 84%.

The NMR spectrum of the citrate salt had the following characteristics:¹H NMR (400 MHz, DMSO-d6) ppm=8.20 (s, 2H), 7.45 (2H, br s), 7.29 (dd,J=7.6, 7.6 Hz, 2H), 7.13 (dd, J=7.2 Hz, J=7.2 Hz ¹H), 7.12 (dd, J=8.0Hz, J=8.0 Hz 2H), 6.86 (d, J=2.4 Hz, 1H), 6.14 (s, 1H), 5.97 (d, J=3.6Hz, 1H), 5.78 (dd, J=12.2, 10.4 Hz, 1H), 4.05 (m, 1H), 4.02 (m, 2H),3.98 (m, 1H), 3.89 (m, ¹H), 2.76 (d, J=15.6 Hz, 2H), 2.66 (d, J=15.6 Hz,2H), 1.16 (d, J=7.2 Hz, 1H).

³¹P NMR (162 MHz, DMSO-d6) ppm=22.29 (s).

¹⁹F NMR (376 MHz, ACETONITRILE-d3) ppm=−133.88 (s).

HRMS: m/z: 507.1561; Calcd for C21H24FN606P: 507.1557.

Anal. Calcd for C₂₁H₂₄FN₆O₆P: C, 46.42; H, 4.62; N, 12.03; P, 4.43; F,2.72. Found: C, 45.83; H, 4.74; N, 11.81; P, 4.45; F, 2.80.

Example 6 Physicochemical Properties of Salts of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate

Representative batches of the malonate, succinate, and citrate salts ofEthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninatewere prepared. The melting points of these salts were determined andserve as a rough measure of stability with a higher melting pointindicating a higher level of stability. As shown in Table 1, the citratesalt had the highest melting point. Additionally, the heat of fusion(ΔH_((fusion))) of each of the three salts is shown in Table 1. Thecitrate salt had the highest heat of fusion indicating a higher degreeof solid-state crystallinity than the other two salts.

TABLE 1 Melting Temperatures and Heat of Fusion of Succinate, Malonateand Citrate Salts of Ethyl N-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]- L-alaninateMolecular ΔH_((fusion)) T_(m) Salt Weight J/g (° C.) Succinate Salt624.52 58.85 138.06 Malonate Salt 610.49 66.10 120.13 Citrate Salt698.56 127.59 149.76

The free base form of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninateis amorphous, hygroscopic and chemically unstable when stored under opencondition at 40° C. and 75% relative humidity (RH). As shown in Table 2,the corresponding succinate, malonate and citrate salts were nothygroscopic at room temperature when exposed to a relative humidity of92% for several days.

TABLE 2 Solid State Hygroscopicity of Salt Forms of EthylN—RS)(1[(2R,5R)- 5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yljoxylmethyl)phenoxyphosphinoyli-L-alaninate at Room Temperature TimeSalt (days) 20-25° C./92% RH Succinate Salt 0 0.01 13 0.010 MalonateSalt 0 0.02 13 0.12 Citrate Salt 0 0.01 25 0.02

The solid-state chemical stability of the free base, succinate, malonateand citrate salts of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninatewere examined under open conditions at 40° C. and 75% relative humidity.As shown in Table 3, the citrate salt displayed superior chemicalstability compared to the succinate and malonate salts.

TABLE 3 Solid State Stability of Free Base form of EthylN—RS)({[(2R,5R)- 5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxylmethyl)phenoxyphosphinoyl]-L-alaninate, and the correspondingSuccinate, Citrate and Malonate Salts at 40° C. 175% Relative HumidityUnder Open Conditions Other Time Free Base Impurities Form (days) (%)(%) Free Base 0 99.01 0.99 7 82.95 17.05 14 66.89 33.11 22 55.90 44.10Succinate Salt 0 98.95 1.05 9 95.15 4.85 16 92.47 7.53 22 90.43 9.57 3085.92 14.08 Malonate Salt 0 97.82 2.18 9 94.66 5.34 16 92.97 7.03 2293.48 6.52 30 85.84 14.16 Citrate Salt 0 98.00 2.00 4 97.27 2.73 1297.20 2.80 17 95.86 4.14 27 94.59 5.41

Example 7 Composition of Tablets Providing Equivalent of 10 mg and 30 mgof EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninateFree Base

The citrate salt of EthylN-RS)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl)oxy}methyl)phenoxyphosphinoyl]-L-alaninatewas formulated into 10 mg and 30 mg tablets using the roller compactionprocess. The active ingredient, lactose anhydrous, microcrystallinecellulose and croscarmellose sodium were first blended, the mixture wasthen lubricated with one third of the total amount of magnesiumstearate, then roller compacted, followed by milling. The resultinggranules were lubricated with the remaining amount of magnesium stearateand pressed into tablets.

Table 4 shows the compositor of tablets that include the citrate salt ofEthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate,and that provide either 10 mg or 30 mg of the free base form of thecompound when the citrate salt dissociates in an aqueous medium.

TABLE 4 Tablet Unit Formula (mg/unit) Compendial 10 mg 30 mg ReferenceFunction Citrate Salt 13.79^(a) 13.79^(a,b) 41.37^(a,c) HSE ActiveIngredient Lactose Anhydrous^(d) 66.00 66.00 198.00 NF Diluent/FillerMicrocrystalline 15.21 15.21 45.63 NF Binder/Filler CelluloseCroscarmellose 3.50 3.50 10.50 NF Disintegrant Sodium Magnesium 1.501.50 4.50 NF Lubricant Stearate Total 100.00 100.00 300.00^(a)Equivalent to 10% 2/2 of free base form of compound. Actual drugsubstance weight will be adjusted to account for drug substance purity.^(b)Equivalent to 10 mg of free base form of compound. ^(c)Equivalent to30 mg of free base form of compound. ^(d)The adjusted drug substancequantity will be subtracted from the quantity of anhydrous lactose.^(e)The abbreviation NF means national formulary, and the abbreviationHSE means House Compendial Reference which is the internal standard usedat Gilead Sciences.

Example 8 Comparison of Lymphocyte Loading of Active Metabolite AfterAdministration to Lymphocytes of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate(Prodrug) or Parent Compound

EthylN-RS)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoylR-alaninateis a prodrug that is hydrolyzed in the human body to yield a hydrolysisproduct that is hereinafter referred to as “the parent compound”. Theparent compound is phosphorylated within the human body to produce abiologically active phosphorylated product (hereinafter “the activemetabolite”) which inhibits the activity of reverse transcriptaseenzyme.

To characterize the intracellular metabolism of the prodrug and parentcompound, lymphocyte cells were treated with either 1 μM prodrug or 100μM parent compound for 2, 6, and 24 hours. Peripheral blood mononuclearcells (PBMCs) were isolated from human huffy coats (Stanford Blood Bank,Palo Alto, Calif.) using centrifugation in Ficoll Paque Plus (GEHealthcare, Piscataway, N.J.) according to manufacturer's procedure.PBMCs isolated from 3 to 4 independent donors were maintained inRPM1-1640 media with 20% fetal bovine serum and antibiotics (quiescentstate) or were activated in the presence of interleukin 2 (20 units/mL,Roche Biochemicals, Indianapolis, Ind.) and phytohemagglutinin PHA-P (1μg/mL, Sigma) for 3 to 4 days before the initiation of experiments.

Human transformed CCRF-CEM T-cells were obtained from The American TypeCulture Collection (Manassas, Va.) and cultured in RPMI-1640 mediumsupplemented with 10% FBS and antibiotics. An aliquot of cells (2−3×10⁶cells) was collected at each time point, counted, pelleted bycentrifugation, resuspended in 0.5 mL of the original treatment mediaand layered onto 0.5 mL of Nyosil M25 oil. The samples were spun in amicrocentrifuge for 20 seconds at the maximum speed (approximately800×g). The top layer of media was removed and the oil layer was washedtwice with 0.8 mL phosphate-buffered saline. Washing buffer and the oillayer were carefully removed, the cell pellet was resuspended in 0.5 mL70% methanol and incubated overnight at −70° C. to facilitate celllysis. Cell lysates were centrifuged, supernatants collected, dried byvacuum and resuspended in 10 μL tetrabutyl ammonium acetate containingthe diphosphate of[5-(6-Amino-purin-9-yl)-2,5-dihydro-furan-2-yloxymethyl]-phosphonic acid(the non-fluorinated analog of the active metabolite) as an internalstandard.

Transient ion-pairing high-performance liquid chromatography coupled topositive ion electrospray tandem mass spectrometery (LC/MS/MS) was usedto quantitate intracellular nucleotides. Methods were adapted from thosedescribed for the acyclic phosphonate nucleotide analog adefovir, itsphosphorylated metabolites and natural nucleotides (Vela, I. E. et al.Simultaneous quantitation of the nucleotide analog adefovir, itsphosphorylated anabolites and 2′-deoxyadenosine triphosphate byion-pairing LC/MS/MS. Journal of Chromatography B Anal. Technol. Biomed.Life Sci., vol. 848, 2007, pp 335-343). Standard curves and qualitycontrol samples were generated for all analytes using extracts fromuntreated cells. Seven point standard curves generally ranged from 0.03to 20 pmol/million cells and had linearity in excess of r² equal to 0.99for all analytes. The lower limits of quantitations for all analytesranged from 0.05 to 0.1 pmol/million cells. Low and high concentrationquality control samples (typically 0.2 and 10 pmol/million cells,respectively) were run with each analyte at the beginning and end ofeach analytical run to assure accuracy and precision within 20%.

The parent compound was incubated at a 100-fold higher concentration(100 μM) than the prodrug (1 μM) to facilitate accurate analysis of themuch lower intracellular accumulation of metabolites observed followingincubation of lymphocytes with the parent compound. As shown in Table 5,the prodrug induced 76-, 290- and 140-fold increased levels of theactive metabolite relative to the parent compound following incubationwith CEM-CCRF, quiescent PBMCs and activated PBMCs, respectively. Activemetabolite levels were normalized based on extracellular concentrationfollowing incubations with 1 μM prodrug or with 100 μM parent compound.

TABLE 5 Dose Normalized Active Metabolite Concentration ((pmol/million)/1 μM media concentration) CEM-CCRF Quiscent PBMC Activated PBMC ParentCompound 0.087 ± 0.014 0.012 ± 0.004 0.045 ± 0.004 Prodrug 6.57 ± 1.003.52 ± 0.96 6.45 ± 1.64 Values represent the mean ± standard deviationof three independent experiments performed in duplicate

Example 9 Comparison of Anti-HIV Activity of the Prodrug and the ParentCompound

The terms “prodrug” and “parent compound” have the meanings set forth inExample 8.

MT-2 cells were maintained in RPMI-1640 medium supplemented withantibiotics and 10% fetal bovine serum (FBS). MT-2 cells were infectedwith HIV-1 IIIB at a multiplicity of infection (moi) of 0.01 and addedto 96-well plates with serial dilutions of tested compounds at a densityof 20,000 cells/well. After a 5-day incubation, the virus-inducedcytopathic effect was determined using a CellTiter-Glo™ cell viabilityassay (Promega, Madison, Wis.) and expressed as a percentage of thesignal from samples with fully suppressed virus replication after thesubtraction of signal from the untreated control. The concentration ofeach drug that inhibited the virus-induced cytopathic effect by 50%(EC₅₀) was determined by non-linear regression. Activity againstNRTI-resistant mutants was determined in parallel with wild-type controlvirus and fold change in EC₅₀ was calculated.

Human peripheral blood mononuclear cells (PBMC) were isolated from donorbuffy coats using centrifugation in Ficoll Paque Plus and activated for4-5 days in RPMI-1640 medium with 20% FBS, antibiotics, interleukin-2(20 units/mL) and phytohemagglutinine PHA-P (1μ/mL). Activated PBMC wereinfected with HIV-1 BaL for 3 hours, washed, seeded into 96-well plates(250,000 cells/well) and incubated with serial dilutions of testedcompounds for 5 days, at which point cell supernatants were collectedand virus production was determined using commercial HIV-1 p24 ELISA(Beckman Coulter, Miami, Fla.). The concentration of each druginhibiting the p24 antigen production by 50% (EC50) was determined byregression analysis.

The effect of the addition of pro-moieties on the anti-HIV activity wasassessed in MT-2 and stimulated PBMC infected with HIV-1. As shown inTable 6, the prodrug was 71- and 2,300-fold more potent than the parentcompound in MT-2 and activated PBMC, respectively.

TABLE 6 Anti-HIV-1 activity of the prodrug and the parent compound in alymphoid derived cell line and primary lymphoid cells. EC₅₀ (μM) MT-2PBMC Parent Compound 10.6 ± 2.4  8.5 ± 7.7 Prodrug 0.15 ± 0.04 0.0037 ±0.0001 Values represent the mean ± standard deviation from at least twodependent experiments performed in triplicate.

Example 10 Oral Bioavailability of the Citrate Salt of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninateAfter Administration in Tablet Form to Beagle Dogs

The dosing group consisted of 3 non-naive male beagle dogs. The animalswere fasted overnight prior to dose administration and up to 4 hr afterdosing. Dogs were administered a single tablet containing 41.38 mg ofthe citrate salt of the prodrug (providing 30 mg of the prodrug pertablet). The tablet consisted of 13.79% of the citrate salt of theprodrug, 66% anhydrous lactose, 15.21% microcrystalline cellulose, 3.5%sodium croscamellose and 1.5% magnesium stearate on a weight per weightbasis. Plasma samples were obtained prior to dosing (0 hr) and at 0.083,0.25, 0.50, 1.0, 2.0, 4.0, 8.0, 12, 24 hr. The blood samples werecollected into Vacutainer™ tubes containing EDTA-K₃. The blood sampleswere centrifuged at 4° C. to separate plasma. An aliquot of μl of eachplasma sample was first diluted with 300 μl 80% acetonitrile/watercontaining 200 nM internal standard. Following centrifugation of theprotein precipitate, 100 μl of the supernatant was removed and used foranalysis. Standard curves and quality control samples were prepared indog plasma from animals not dosed with the prodrug. Samples wereanalyzed by a partially validated liquid chromatography couple to triplequadrupole mass spectrometry method.

Administration of the citrate salt of the prodrug as a tablet resultedin rapid absorption of the prodrug and the parent compound derived fromthe prodrug. As summarized in Table 7, plasma exposure to the prodrugand the parent compound was observed following administration. The oralbioavailability of intact prodrug was 11.4%. These results were notmarkedly different from those observed following oral administration ofthe prodrug in a solution formulation, illustrating the effectiveness ofthe tablets containing the citrate salt of the prodrug to deliver theprodrug and its metabolites into the systemic circulation.

TABLE 7 Mean Plasma Pharmacokinetic Parameters for the Prodrug and theParent Compound Following Oral Administration of a Tablet Formulation ofthe Citrate Salt of the Prodrug at a mean dose of 3.05 mg/kg equivalents(Mean, n = 3) Value Value Parameter Prodrug Parent Compound T_(max) (hr)0.58 2.33 C_(max) (nM) 1,560 959 AUC_(o-t) (nM · hr) 587 7,600 AUC₀₋₈(nM · hr) 608 9,630 t_(1/2) (hr) 0.289 11.7 % F^(a) 11.4 Not Determined^(a)Calculated based on a mean plasma AUC_(o-t) of 818 nM · hr observedfollowing a 30 minute intravenous Infusion of 0.5 mg/kg GS-9131 tobeagle dogs.

Example 11 Differential Scanning Calorimetry (DSC) of Citrate, Malonateand Succinate Salts of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate

Differential scanning calorimetry accurately measures temperatures andheat flow associated with thermal transitions in a material. The DSCtraces of the inventive salts of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]L-alaninatewere generated using a TA Instrument (New Castle, Del.) DSC 2010 at ascan rate of 5° C. min⁻¹. FIG. 1 shows the characteristic DSC trace forthe malonate salt of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate.The DSC thermogram revealed a single endotherm corresponding to themelting point (120.43° C., ΔH_(f)=73.72 J/g) followed by a singleexotherm corresponding to the decomposition of the malonate salt.

FIG. 2 shows the characteristic DSC trace for the succinate salt ofEthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate.The DSC thermogram of the succinate salt of GS-9131 revealed a singleemdotherm corresponding to the melting point (137.44° C., ΔH_(f)=66.18J/g) followed by a single exotherm corresponding to the decomposition ofthe salt.

FIG. 3 shows the characteristic DSC trace for the citrate salt of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate.The DSC thermogram of the citrate salt revealed a single endothermcorresponding to the melting point (149.41° C., ΔH_(f)=85.72 J/g)followed by a single exotherm corresponding to the decomposition of thecitrate salt.

The citrate salt has a significantly greater heat of fusion than themalonate and succinate salts, indicating a higher degree of solid-statecrystallinity.

Example 12 X-Ray Diffraction (XRD) Analysis of the Citrate, Malonate andSuccinate Salts of EthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninate

The X-ray powder diffraction (XRPD) patterns of the inventive salts ofEthylN-[(S)({[(2R,5R)-5-(6-amino-9H-purin-9-yl)-4-fluoro-2,5-dihydrofuran-2-yl]oxy}methyl)phenoxyphosphinoyl]-L-alaninatewere generated using two methods. In the first method, a Shimadzu XRD6000 instrument with the following attributes was used: Cu X-ray tube,2.2 KW, NF (normal focus); monochromator curved graphite; goniometervertical, 185 mm radius; divergence slits: 0.5°, 1.0°, 0.05 mm; sollerslits: 0.05°, 1°, 2°; receiving slits: 0.15 mm, 0.3 mm; scintillationdetector (NaI) HV 500-1200.

In the second method, a Shimadzu XRD 6000 instrument with the followingattributes was used: Cu target X-ray tube, 35 kv, current 40 ma;continuous scan, monochromator, divergence slit, 1°; soller slit 1°,receiving slit 0.3 mm.XRPD data for the malonate and succinate salts were obtained usingmethod 1. XRPD data for the citrate salt was obtained using method 2.

It is understood that experimental deviations can slightly change theXRPD absorption band (peak) information. Thus, the numbers reported inthis patent resulting from XRPD patterns of the inventive salts will bethe same or essentially the same as the numbers which will occur uponrepeating the tests. “Essentially the same” in this context means thattypical peak position and intensity variability are taken into account(as they normally would be for any analytical technique). For example,one skilled in the art will appreciate that the peak positions will showsome inter-apparatus variability. For example, the 2-theta peakpositions typically deviate by as much as 0.1 degrees. Further, oneskilled in the art will appreciate that relative peak intensities willalso show variability due to the degree of crystallinity, preferredorientation, prepared sample surface, and other factors known in theart. Thus, the relative peak intensities should be taken as qualitativemeasure only.

FIG. 4 shows the characteristic XRPD pattern for the malonate salt. Theprincipal and characteristic peaks that define this crystalline form ofthe malonate salt are shown in Tables 8A and 8B.

TABLE 8A Malonate Salt PXRD Peaks Strongest Peaks 2Theta (deg) d (A)FWHM (deg) Integrated Int 1 17.76 4.9912 0.3190 16049 2 14.92 5.93420.3023 14513 3 18.80 4.7163 0.6572 21597

TABLE 8B *** Basic Data Process *** Group Name Data Name 34984B FileName 34984B.PKR Sample Name Lot# 2587-168-17 Comment     Salts    USP<941> # Strongest 3 peaks Integrated peak 2Theta d FWHM Intensity Intno. no. (deg) (A) I/I1 (deg) (Counts) (Counts) 1 13 17.7561 4.99119 1000.31900 947 16049 2 12 14.9168 5.93423 92 0.30230 867 14513 3 15 18.80004.71634 80 0.65720 758 21597 # Peak Data List peak 2Theta d FWHMIntensity Integrated Int no. (deg) (A) I/I1 (deg) (Counts) (Counts) 14.7340 18.65124 1 0.16140 9 69 2 5.9215 14.91331 11 0.26490 100 1723 37.0000 12.61783 3 0.20660 29 563 4 7.5504 11.69922 29 0.44910 279 6489 59.1500 9.65724 8 0.42000 76 1779 6 10.5600 8.37073 4 0.18660 34 468 711.0208 8.02175 34 0.29110 323 4468 8 11.1600 7.92200 30 0.56800 2877708 9 12.6400 6.99756 16 0.35600 147 2545 10 12.8400 6.88901 20 0.27840191 2234 11 14.5200 6.09549 9 0.16800 87 1282 12 14.9168 5.93423 920.30230 867 14513 13 17.7561 4.99119 100 0.31900 947 16049 14 18.30004.84405 73 0.40260 692 12656 15 18.8000 4.71634 80 0.65720 758 21597 1619.2077 4.61714 41 0.36220 387 6608 17 19.5800 4.53018 63 0.34720 59311731 18 20.0200 4.43159 14 0.15560 130 1783 19 20.7824 4.27071 240.54170 223 6510 20 22.0112 4.03499 26 0.47750 250 6040 21 22.48003.95190 22 0.45260 211 4333 22 23.3273 3.81023 18 0.29470 171 2718 2324.1490 3.68242 24 0.51800 232 6302 24 25.3800 3.50653 44 0.43120 41314100 25 25.8930 3.43821 44 0.27980 419 5539 26 26.2380 3.39378 240.79670 227 8510 27 26.8200 3.32144 40 0.61720 383 13675 28 27.30873.26310 14 0.49680 130 3097 29 27.7600 3.21107 18 0.42180 175 4291 3028.9185 3.08501 27 0.54570 258 5924 31 29.3200 3.04367 11 0.30660 1042031 32 30.3600 2.94173 13 0.65340 119 4194 33 31.1400 2.86980 170.56000 159 4356 34 32.0000 2.79461 3 0.14140 25 165 35 32.8233 2.7263710 0.39330 95 1976 36 33.8725 2.64428 7 0.55500 64 1859

FIG. 5 shows the characteristic XRPD pattern for the succinate salt. Theprincipal and characteristic peaks that define this crystalline form ofthe succinate salt are shown in Tables 9A and 9B.

TABLE 9A Succinate Salt PXRD Peaks Strongest Peaks 2Theta (deg) d (A)FWHM (deg) Integrated Int 1 24.91 3.5716 1.1300 40991 2 18.46 4.80243.7340 16639 3 17.76 4.9901 3.4162 9106

TABLE 9B *** Basic Data Process *** Group Name Data Name 34984A FileName 34984A.PKR Sample Name Lot# 2587-166-27 Comment     Salts     USP<941> # Strongest 3 peaks Integrated peak 2Theta d FWHM Intensity Intno. no. (deg) (A) I/I1 (deg) (Counts) (Counts) 1 10  24.9100 3.57161 1001.13000 590 40991 2 7 18.4600 4.80243 81 0.73400 480 16639 2 6 17.76004.99010 79 0.41620 464  9106 # Peak Data List peak 2Theta d FWHMIntensity Integrated Int no. (deg) (A) I/I1 (deg) (Counts) (Counts) 16.0033 14.71029 7 0.64670 43 1492 2 9.4308 9.37032 12 1.24830 69 4432 311.7717 7.51169 33 1.08060 195 11923 4 14.7400 6.00500 10 0.60000 604288 5 16.0720 5.51020 9 0.55880 56 1470 6 17.7600 4.99010 79 0.41620464 9106 7 18.4600 4.80243 81 0.73400 480 16639 8 20.4772 4.33367 570.87020 337 13869 9 21.4293 4.14323 43 0.40730 252 4832 10 24.91003.57161 100 1.13000 590 40991 11 26.1400 3.40628 36 2.92000 212 21458 1227.9400 3.19079 15 1.47000 86 8157 13 29.7800 2.99769 9 0.31340 53 77914 30.9200 2.88972 7 1.28000 40 3619 15 33.2233 2.69446 8 1.08670 492527

FIG. 6 shows the characteristic XRPD pattern for the citrate salt. Theprincipal and characteristic peaks that define this crystalline form ofthe citrate salt are shown in Tables 10A and 10B.

TABLE 10A Citrate Salt PXRD Peaks Strongest Peaks 2Theta (deg) d (A)FWHM (deg) Integrated Int 1 19.81 4.4784 0.2635 14837 2 28.63 3.11550.3312 13074 3 14.64 6.0465 0.2473 10572

TABLE 10B *** Basic Data Process *** Group Name Data Name 35614A FileName 35614A.PKR Sample Name Lot# 2782-78-32 Comment         USP <941> #Strongest 3 peaks Integrated peak 2Theta d FWHM Intensity Int no. no.(deg) (A) I/I1 (deg) (Counts) (Counts) 1 21 19.7856 4.48352 100 0.268101443 20538 2 30 23.8400 3.72944 55 0.33400 793 14567 3 35 26.59653.34884 51 0.31810 734 11131 # Peak Data List peak 2Theta d FWHMIntensity Integrated Int no. (deg) (A) I/I1 (deg) (Counts) (Counts) 16.7400 13.10398 3 0.16360 47 456 2 6.9496 12.70922 6 0.21930 87 864 38.2200 10.74764 6 0.23120 81 1414 4 8.4436 10.46352 18 0.22630 253 28025 9.0566 9.75662 6 0.22460 89 1275 6 11.0600 7.99341 4 0.18000 62 762 711.2871 7.83308 16 0.23720 238 2770 8 11.8800 7.44345 4 0.19560 52 603 912.0508 7.33833 8 0.25030 114 1167 10 13.1691 6.71758 16 0.22170 2293085 11 13.9959 6.32255 25 0.23910 358 5182 12 14.6151 6.05604 330.26400 470 7221 13 15.4624 5.72604 25 0.30010 356 5658 14 15.82005.59740 3 0.18800 48 832 15 16.9600 5.22364 26 0.27100 377 5496 1617.3474 5.10785 46 0.26120 668 9289 17 18.0000 4.92411 19 0.19920 2713037 18 18.2200 4.86514 32 0.20420 465 5224 19 18.7154 4.73746 4 0.2142051 606 20 19.2200 4.61421 10 0.19200 146 2871 21 19.7858 4.48352 1000.26810 1443 20538 22 20.0800 4.41849 38 0.19380 546 6060 23 20.53154.32233 32 0.32250 455 7724 24 21.1200 4.20320 8 0.25500 114 1667 2521.4000 4.14863 16 0.26760 235 3054 26 21.8913 4.05682 10 0.26260 1412250 27 22.8001 3.89713 13 0.30110 181 2641 28 23.2200 3.82760 3 0.1976050 746 29 23.3691 3.80351 6 0.16040 83 625 30 23.8400 3.72944 55 0.33400793 14567 31 24.1800 3.67776 26 0.12300 380 4146 32 25.0296 3.55482 80.32290 119 2002 33 25.6031 3.47648 7 0.22090 102 1365 34 26.28003.38845 26 0.30180 379 5681 35 26.5965 3.34884 51 0.31810 734 11131 3627.4848 3.24259 6 0.20170 83 1222 37 28.1600 3.16636 4 0.09340 58 441 3828.5989 3.11875 46 0.33280 666 12909 39 29.0484 3.07151 9 0.23960 1271440 40 29.5600 3.01950 20 0.48340 290 6624 41 29.8800 2.98789 160.14600 235 2012 42 30.4400 2.93419 3 0.09340 44 274 43 30.7800 2.9025411 0.10020 155 737 44 31.0600 2.87701 16 0.19060 233 3504 45 31.34002.85195 4 0.18000 55 802 46 31.5800 2.83082 4 0.12960 54 357 47 31.86022.80656 12 0.36550 172 2804 48 32.2200 2.77603 4 0.08580 55 482 4933.0800 2.70580 3 0.09060 50 388 50 33.2668 2.69103 5 0.12920 65 453 5133.5921 2.66571 7 0.36940 108 2008 52 34.3755 2.60673 6 0.15550 83 1053

All literature and patent citations above are hereby expresslyincorporated by reference at the locations of their citation.Specifically cited sections or pages of the above cited works areincorporated by reference with specificity. While the invention has beendescribed in detail sufficient to allow one of ordinary skill in the artto make and use the subject matter of the following claims, it is alsocontemplated that certain modifications of the following claims can bemade and yet remain within the scope and spirit of the invention.

1. A citrate salt of formula I or a hydrate thereof:


2. The salt or hydrate of claim 1, characterized by being crystalline.3. The salt of claim 2, characterized by spectral d-spacing absorptionbands obtained from an X-ray powder diffraction pattern of the same oressentially the same as 4.48, 3.12 and 6.05 angstroms.
 4. The salt ofclaim 2, characterized by 2-theta diffraction angle absorption bandsobtained from an X-ray powder diffraction pattern of the same oressentially the same as 19.81, 28.63 and 14.64 degrees.
 5. The hydrateof claim 2, characterized in being partially or fully hydrated.
 6. Thesalt of claim 2, characterized in being anhydrous or essentiallyanhydrous.
 7. A pharmaceutical composition comprising a therapeuticallyeffective amount of the salt or hydrate of claim 1 and apharmaceutically acceptable carrier or excipient.
 8. The pharmaceuticalcomposition of claim 7, further comprising an additional therapeuticagent.
 9. The pharmaceutical composition of claim 8, wherein theadditional therapeutic agent is an anti-HIV drug.
 10. The pharmaceuticalcomposition of claim 7, wherein the pharmaceutical composition is in aunit dosage form.
 11. The pharmaceutical composition of claim 10,wherein the unit dosage form is a tablet.
 12. A pharmaceuticalcomposition prepared by combining a therapeutically effective amount ofthe salt or hydrate of claim 2 with a pharmaceutically acceptablecarrier or excipient.
 13. A method of treating or prophylacticallypreventing HIV, comprising administering to a human in need thereof atherapeutically effective amount of the salt or hydrate of claim
 1. 14.A succinate salt of formula II or a hydrate thereof:


15. The salt or hydrate of claim 14, characterized by being crystalline.16. The salt of claim 15, characterized by spectral d-spacing absorptionbands obtained from an X-ray powder diffraction pattern of the same oressentially the same as 3.57, 4.80 and 4.99 angstroms.
 17. The salt ofclaim 15, characterized by 2-theta diffraction angle absorption bandsobtained form an X-ray powder diffraction pattern of the same oressentially the same as 24.91, 18.46 and 17.76 degrees.
 18. Apharmaceutical composition comprising a therapeutically effective amountof the salt or hydrate of claim 14 and a pharmaceutically acceptablecarrier or excipient.
 19. The pharmaceutical composition of claim 18,further comprising an additional active ingredient.
 20. A pharmaceuticalcomposition prepared by combining a therapeutically effective amount ofthe salt or hydrate of claim 15 with a pharmaceutically acceptablecarrier or excipient.
 21. A method of treating or prophylacticallypreventing HIV, comprising administering to a human in need thereof atherapeutically effective amount of the salt or hydrate of claim
 14. 22.A malonate salt of formula III or a hydrate thereof:


23. The salt or hydrate of claim 22, characterized by being crystalline.24. The salt of claim 23, characterized by spectral d-spacing absorptionbands obtained from an X-ray powder diffraction pattern of the same oressentially the same as 4.99, 5.93 and 4.72 angstroms.
 25. The salt ofclaim 23, characterized by 2-theta diffraction angle absorption bandsobtained from an X-ray powder diffraction pattern of the same oressentially the same as 17.76, 14.92 and 18.80 degrees.
 26. Apharmaceutical composition comprising a therapeutically effective amountof the salt or hydrate of claim 22 and a pharmaceutically acceptablecarrier or excipient.
 27. The pharmaceutical composition of claim 26,further comprising an additional active ingredient.
 28. A pharmaceuticalcomposition prepared by combining a therapeutically effective amount ofthe salt or hydrate of claim 23 with a pharmaceutically acceptablecarrier or excipient.
 29. A method of treating or prophylacticallypreventing HIV, comprising administering to a human in need thereof atherapeutically effective amount of the salt or hydrate of claim 22.